Support structure for surface heating units



1961 E. w. BARNES ETAL 2,996,598

SUPPORT STRUCTURE FOR SURFACE HEATING UNITS Filed June 29, 1960 FIG. I 36.2

INVENTORS: EMMETT'W. BARNES ROBERT E. SAND ATT'Y United States Patent 2,996,598 SUPPORT STRUCTURE FOR SURFACE HEATING UNITS Emmett W. Barnes, Lombard, and Robert E. Sand, Itasca,

Ill., axignors to General Electric Company, a corporation of New York Filed June 29, 1960, Ser. No. 39,684 8 Claims. (Cl. 7:19-37) This invention relates to surface heating units in which tubular sheathed electric heating elements are arranged in a flat spiral form, and more particularly to support structures for these units.

The structure shown herein has been designed to provide an electric range surface heating unit support structure which has a rigid central support portion which forms a primary supporting structure while affording means for adequately supporting the outermost convolutions of the heating unit. The central support comprises a Y member or sub-structure which substantially traverses the diameter of the heating unit assembly to insure structural rigidity. For larger sized heating units, this central member must be braced. This bracing has formerly been secured by affixing projections of the central support members into a surrounding trim ring structure to form the entire unit into a single member. Recently, the tendency has been to utilize a trim ring with no connection to the unit so that each may be removed separately for individual cleaning. In such a unit, the central support must then be braced by other support members.

For the present embodiment, a pentagonal outer substructure has been evolved. In combination with the Y support, the pentagon sides form a truss structure which gives substantial strength to the central Y support, and also provide radially extending legs on which the outermost of the heating coils may be properly supported. In this way, a very substantial outer support is formed. Usually in electric ranges, the inner convolutions of a surface heating unit have a rather concentrated heating pattern, and it is also the practice to arrange a heating unit with the inner coil portions and the outer coil portions separately energizable, whereupon according to the operating conditions the components of the supporting structure will tend to expand individually in proportion to the temperature rise which each component experiences. With rigid permanent connections between the sub-structures there would be distortion of the weaker section due to the individual expansions and the con sequent unresolved stresses, whereupon the convolutions of the heating unit would be distorted out of their common operating plane. To prevent the possibility of such distortion, the present invention has provided an expansion joint at a major point of joinder of the two substructures. At this point, certain of the pentagon members extend radially on each side of the base leg of the Y structure. The latter element is slotted to accommodate the passage of a rivet by means of which the pentagon members and the Y base member are secured together. In this way, relative movement of the Y member with respect to the outer sub-structure is permitted without the possibility of distortion and without the loss of rigidity.

It is therefore an object of the present invention to provide a support for a surface heating unit which includes a rigid central support traversing the diameter of the structure and an outer structure having radial extensions and serving as bracing for the inner support;

all of the points of junction between the inner and outer supports being of the permanent type except for a single expansion joint between the supports.

Itis a vfurther object of the invention to provide-in;

Patented Aug. 15, 1961 a surface heating unit spider, a Y shaped central structure formed of two angled members commonly joined in a single leg and a pentagon structure bracing the Y, and of which both structures extend in the same plane. The pentagon bracing members each terminate in radial extensions which provide further support for the heating unit coil. All junction points in the spider are permanent with the exception of the point of joinder of the pentagon legs to the common Y joint, which joint is formed in a manner allowing relative movement of the Y with respect to the pentagon.

Other objects, features and advantages of the invention will be apparent from the detailed description of the presently preferred embodiment thereof, read in connection with the accompanying drawings in which:

FIG. 1 is a bottom view of a heating unit employing the present support structure;

FIG. 2 is a side sectional view of the unit taken along the lines 2-4.: of FIG. 1 and shows the unit resting in its normal position on a cooking top as a range surface unit; and

FIG. 3 is an exploded view of the support structure components within the dotted enclosure 3 in FIG. 1.

In the typical installation, the heating units are mounted in a conventional electric range having a cooking top 11 provided with a number of suitable circular openings '12. each adapted to receive a cooking unit 13. Usually there are four or less of such cooking units suitably arranged about the cooking top.

Each cooking unit as shown in FIGS. 1 and 2 generally comprises a first sheathed heating element 14 having respective terminal portions 15 and 16 and a second sheathed heating element 17 having the terminal portions 18 and 19. Preferably, these elements will be constructed as described in the United States Patent to C. C. Abbott, No. 1,367,341, dated February 1, 192.1, and in the I. C. Sharp Reissue Patent No. 22,177 of September 8, 1942. Each of these elements, as described in the cited patents, has a coiled resistance conductor housed in a metallic sheath and supported in uniformly spaced relationship to the sheath by a highly compacted mass of a suitable heat conducting and electrically insulating material such as powdered magnesium oxide. As is conventional, the heating elements are arranged to form flat spirals of several convolutions and are nested one within the other on a support structure 20. The support structure of the present invention includes a plurality of radially extending arranged support plates as will be described more fully later. It is sufiicient to state at this time that the upper edges of these support plates lie in a common plane and provide a support platformfor the heating elements as shown. Suitable connectors (not shown) of any known design may be used to connect the terminal portions to a source of electrical power.

The structure 20 is carried by a trim ring 25 having a rim 2:6 resting on the cooking top 11 about the opening therein and a downwardly extending circular sidewall flange 27 which is spaced inwardly from the depending flange 28 defining the cooking top opening 12. The flange 27 terminates at its lower extremity in an inwardly directed flange 29. In the present embodiment there is no permanent connection between the trim ring and .the support structure although the radial extensions of'the structure norm-ally rest on an inwardly directed flange 29 of the trim ring as will be explained more fully later. The trim ring thus establishes the plane of the upper edges of the support plates parallel to the plane of the cooking top 11. A suitable drip and reflector pan 30 also may be removably supported below the heating unit as required.

Referring more specifically to the support structure20,

' as shown best inFIG. 1, there may be seen the central .minal ends. .one another and meet at the coil center section to there- 3 Y portion for-med by the angled plates 31 and 32. It may be seen that these plates are in spaced-apart relationship at the end of the heating unit adjacent the ter- These plates 31 and 32 are canted toward afterextend in parallel to form the common Y leg 33. Within the common Y leg portion, the separate plates are welded together or secured in some other suitable of the heating units,'an outer pentagonal support structure is arranged to brace the central Y support. This pentagon includes five strut members 35, 36, 37, 38 and 39 respectively. The strut members are joined to combinedly form an outer peripheral coil support about the Y, and, of course, members 35 and 36 combine with member 31 to form a truss-like structure of strength. A similar truss is formed by the other elements. Each of the struts has radial extensions extending at obtuse angles from its central portion. For example, on strut 35 there a first extension 35.1 extending angularly from the central section of the strut and which is coextensive and co-terminal with radial extension 31.1 of the Y member and is rigidly secured thereto as by welding. The other radial extension of strut 35, which is numbered 35.2,

is similarly formed and is secured to the extremity 36.2 of the adjacent strut 36. This same pattern of fixed connection of adjacent extensions is continued throughout the pentagon structure with the exception of the connection of the common Y leg 33 to the adjacent radial extensions 36.1 and 37.1. This last named connection rests on the outer edge of its horizontal rim 26. The support structure and its appendant heating coils rest on the inwardly directed lower flange 29 of the trim ring within circular opening 12. At the lowermost portion of the circular sidewall of the opening there is the aforementioned inwardly directed fiange 56 on which rests the drip pan or reflector 30. By utilizing this form of construction the trim ring, the heating coil and the drip pan may each be removed independently of the other components.

A support structure embodying the present invention has substantial advantages. When the respective heating coils are energized by current from the electrical source, a considerable amount of heat is generated. Since the heating coilsare aflixed to the Y leg by the jaws previously described, direct heat transfer is made from the heating coil to the Y leg 33. Further, the Y structure is located more centrally within the heating coil, thus is closer to the area of greatest heat concentration. The Y structure will then expand proportionately to the heat which it receives. The outer pentagon has less direct heat transfer with the heating coils and will not heat to the same extent as the Y structure. The pentagon will :expand proportionately to the amount of heat directed to it which, as mentioned in most instances, will be less than the amount of heat directed to the Y structure. The

pentagon will therefore expand at a rate independent of the rate of expansion of the Y structure. With the slotted relationship of the Y leg to the rivet, the Y leg may expand independently of the pentagon. The slots under this set of circumstances will tend to move horizontally ,withrespect to the rivet shank 54 and as a result the Y leg is expansible independently of the expansion of the 1 adjacent pentagon strut extensions. The expansion joint is shown best in FIG. 3. As mentioned previously, plates 31 and 32 are permanently joined together along the common Y leg 33. One of these plates, plate 32, has upwardly extending projections such as 45 and 46 which provide jaws to grip the sheath of the outer heating element 14. A similar set of jaws is formed by projection 47 and a mating projection (not shown) which grips the inner heating coil 17 along its outer convolution. In

' this manner, each of the heating units is gripped solidly by the support structure at one place and one place alone, providing freedom of movement, as disclosed in Vallorani et al. 2,662,158, issued December 8, 1953.

For the purpose of joining the pentagonal structure to the Y structure, each Y plate 31 and 32 has a horizontal slot, respectively 50 and 51, aligned adjacently. Positioned on each side of these Y leg members are the respective pentagon strut extensions 36.1 and 37. 1. Each of these extensions has formed therein a circular hole, 37.3 and 36.3. These holes are aligned with the slots 50 and 51 in the adjacent Y leg members. These holes accommodate a rivet 52 which has a head portion 53 and a shank portion 54. In assembling, this shank portion 54 is fitted through hole 36.3, slot 51, slot 50 and hole 37.3 and the shank end of the rivet is peened over outwardly of plate 37.1. The rivet head 53 thus abuts strut extension 36.1 and the peened over shank abuts extension 37.1 thus expansibly joining the Y structure and the pentagon structure. From FIG. 3 it can also be readily seen that each of the plates and struts has formed at its outermost tip a shoulder such as 36.5 on bar 36 which rests on the inwardly turned flange 29 of the trim ring to support the unit and its support structure.

The relative position of the parts as they rest on a cooking top may best be seen in FIG. 2 which shows a cooking top 11 having an opening 12 defined by vertical sidewall 28 which at its base terminates at an inwardly directed flange 56. Resting on the cooking surface about the circular opening 12 is the trim ring 25. The trim ring thus formed allows relative expansion of the two sections of the support structure without warping of the parts.

It has previously been noted that in electric ranges using the two-coil heating units, it is possible to energize the respective coils independently. By means of the present invention, it makes no difference which is heated, as respects the maintenance of the planar alignment of 'the support structure elements. The support structure functions with equal efliciency if a particular mode of heating unit operation causes the outer structure to heat more intensely than the central Y member. The relative movement between the sections is possible in either direction along the plane of the common Y leg; and the expansion joint does not interfere with the required rigidity of the support structure.

It will also be observed that the present invention in sures the proper spacing of the convolutions of the intertwined or adjacent heating elements under all operating conditions, for each heating element is secured to one, only, of the sub-structures, and to that portion of the substructure most likely to be at a substantial temperature difierence relative to the other sub-structure, where upon the heating coils may freely move over the supporting structures without buckling or warping. It should be noted that although a two-element unit has beenshown theprinciple would apply where one, two or three heating elements are combined to form a single cooking unit While there has been described what is presently con sidered to be the preferred embodiment of the invention it will be understood that various modifications may hi made therein, and it is intended to cover in the appendet claims all such modifications as fall within the true spiri and scope of the invention.

What is claimed is:

1. A support structure for a heating unit of the typ having a sheathed heater coiled in a horizontal plane said structure comprising a. first sub-structure, a pluralit of members in said first sub-structure each substantiall traversing the diameter of said heater coil, means fc permanently securing said heater to said sub-structure z erally reinforcing said first structure, means for permanently afiixing said first sub-structure to said second substructure at all radial positions on said first sub-structure save said heater secured position, and an expansion joint connection between said first and second sub-structures at said heater secured position.

2. A support structure as claimed in claim 1 in which said expansion joint comprises a rivet secured to said second sub-structure and fitted through slots in said first substructure members to allow relative planar movement of said sub-structures.

3. A support structure for a heating unit of the type having a sheathed heater coiled in a horizontal plane, said structure comprising a first substructure, a plurality of members in said first sub-structure each substantially traversing the diameter of said heater coil, two of said members commonly joined at a single position radial to said coil, means for permanently securing said heater to said sub-structure at the commonradial joint, a second sub-structure for peripherally reinforcing said first substructure, said second sub-structure comprising a plurality of strut members formed in substantially pentagonal configuration, means for permanently 'afiixed said first substructure to said second sub-structure at all corners of said pentagon save said common radial joint, and an expansion joint connection between said first and second sub-structures at said common radial joint, comprising a rivet secured to said second sub-structure members and fitted through slots in said first sub-structure members to allow relative planar movement between said sub-structures.

4. An 'electric surface heating unit comprising a sheathed heater bent to form a planar horizontal cooking surface, a support structure disposed in a plane below said heater, said support structure comprising an inner Y shaped support section and an outer section, said Y section including an apex leg and two other legs all extending radially from said unit in the plane of said support structure, said outer support section comprising a plurality of reinforcing struts joined to said Y legs, means for supplying electric current to said heating unit to heat said unit, said unit on heating supplying heat in difiering proportions to said inner and outer support structure sections, means for permanently securing said heater only to said apex leg, expansion joint means between said apex leg and the struts joined thereto to allow for expansion of said inner and outer sections at different rates responsive to' the different proportions of heat supplied to said sections.

5. An electric surface heating unit comprising a sheathed heater bent to form a planar horizontal cooking surface, a support structure disposed in a plane below said heater, said support structure comprising an inner Y shaped support section and an outer section, said Y section including an apex leg and two other legs all extending separately from said unit in the plane of said support structure, said outer support section comprising a plurality of reinforcing struts joined to said Y legs, said struts forming a pentagonal configuration about said inner section, means for supplying electric current to said heating unit to heat said unit, said unit on heating supplying heat in differing proportions to said inner and outer support sections, means for permanently securing said heater only to said apex leg, expansion joint means between said apex leg and the struts joined thereto to allow for expansion of said inner and outer sections at different rates responsive to the different proportions of heat supplied to said sections, said expansion joint comprising a rivet and slot joint with a slot in said apex leg to allow movement of said apex leg relative to said struts.

6. An electric surface heating unit comprising a sheathed heater configurated to form a planar horizontal cooking surface, a planar support structure disposed below said heater, said support structure comprising an inner Y shaped support section and an outer section, said Y section including two angled members joined to form a common apex leg, said angled leg members extending separately from said unit in the plane of said support structure, an outer support structure comprising a plurality of reinforcing struts joined to said Y leg members, each of said struts terminating in members extending from said support structure beneath said heating unit, means for supplying electric current to said heating unit to heat said unit, said unit when heating supplying heat in differing proportions to said inner and outer support sections, means for securing said heater to one of said members at said apex leg, expansion joint affixation means between said common apex leg and the radial extension members of said struts joined thereto to allow relative movement between said inner and outer sections in response to the heat supplied from said heater.

7. A support structure for a heating unit of the type having a sheathed heater coiled in a horizontal plane, said structure comprising a first sub-structure, a plurality of members in said first sub-structure each substantially traversing the diameter of said heater coil for supporting said heater coil thereon, a second sub-structure for peripherally reinforcing said first structure, members extending radially from each of said sub-structures, means for permanently securing said heater to only one of said sub-structures at one radial extension position, means for permanently aflixing said first sub-structure extending members to said second sub-structure members at all radial extension positions save said one position, and an expansion joint connecting said first and second substructure members at said one position to allow relative movement between said sub-structures.

8. An electric surface heating unit comprising a sheathed heater coiled to form a planar horizontal cooking surface, a support structure disposed in a plane below said heater, said support structure comprising an inner Y shaped support section and an outer section, said Y section including an apex leg and two other legs all extending radially from said coiled heater in the plane of said support structure, said outer support section comprising a plurality of reinforcing struts, integral legs extending radially from each of said struts and joined to said Y legs, all said legs positioned to support thereon said heater coil, means for supplying electric current to said heater coil to heat said unit, said unit when heating supplying heat in differing proportions to said inner and outer support sections, means for permanently securing said heater to one of said legs at said apex leg extension, expansion joint means between said apex leg and the strut legs joined thereto to allow for expansion of said inner and outer sections at different rates responsive to the different proportions of heat supplied to said sections.

References Cited in the file of this patent UNITED STATES PATENTS 2,271,977 Hielmgren Feb. 3, 1942 2,413,478 Wiegaud Dec. 31, 1946 2,662,158 Vallorani et al. Dec. 8, 1953 

